Conductive shoe method of making same



Dec. 20, 1966 J. H. FISCHER I OONDUCTIVE SHOE METHOD OF MAKING SAMEFiled April .24, 1964 ww ww BYQMQM ATTORNEY States atent 3,293,494CONDUCTIVE SHGE METHOD F MAKING SAME Joseph H. Fischer, Woodbury, Conn.,assigner to United States Rubber Company, New York, NSY., a corporationof New Jersey Filed Apr. 24, 1964, Ser. No. 362,222 8 Claims. (Cl.317-2) This invention relates to an electric-ally conductive shoe and,more particularly, .to a sole construction for a shoe that Iprovides anelectrical grounding path for the wearer. The invention also relates tonovel methods for the production and manufacture of the improved shoe.

Heretofore, the vast majority of conductive shoes were m-ade withentirely conductive soles and/or heels, thus, requiring a great ramountof conductive material. This material, such as conductive rubber, wasvery expensive and, thus, great-ly increase-d the cost of the shoe.

Successful attempts have been made to produce `a conductive shoe havinga non-conductive sole equipped with conductive inserts for providing anelectrical path between the ground and the wearers foot. One such shoeconstruction was shown in United States Patent No. 2,710,366, issued onJune 7, 1955, to J. S. Stern, Jr., et al., wherein a thick conductiverubber plug was inserted into a wooden heel to provide contact betweenthe wearer and the ground. The plug was securely held in place by thelong bearing surface between the wooden heel and the plug. Furthermore,the rigidity of the heel prevented the plug from bending and workingloose from the heel.

A similar type plug was found to be ineffective when adapted for usewith a relatively ilexible, thin soled shoe, such as a sneaker or thelike. The continual llexing of such a sole provides bending force at theplug and outsole interface that tend -to loosen the bond and may resultin a removal of the plug from the outsole.

Accordingly, it is an object of this invention to provide an improvedconductive sole construction and method of making same.

Another object is to provide an improved conductive plug for a flexiblenon-conductive sole construction.

A further object is to provide a conductive sole construction that isextremely simple and inexpensive to fabricate and, yet, results in anintegral unit with Iwe-araresisting qualities.

These yand other objects are accomplished in accordance with thisinvention which comprises a non-conductive outsole having yan apertureextending therethrough, a non-metallic flexible conductive plug in saidaperture, the plug having a ground engaging surface and an innersur-face, the ground engaging s-urface having an inwardly extendinggroove forming an outer plug portion that is securely bon-ded to theoutsole and a central flexible plug portion; and conductive meansinterconnecting the inner plug surface with the innermost portion of theshoe, so that, the conductive means and the plug form an electricalgrounding path for the wearer.

In accordance with the preferred method of making the Iabove soleconstruction, the plug is placed into the outsole aperture and the-groove is pressed or cut into the plug surface to from an annular plugportion and a central flexible plug portion; the pressing step iseffective to force the ann-ular plug .portion firmly against the innerperiphery of the -outs-ole aperture and to force the inner plug surfacermly against a gum layer that overlies the inner portion of the outsole.The entire assembly is then vulcanized to form a molecular bond betweenthe conductive plug and the adjacent rubber surfaces.

For a better understanding of the present invention together with otherand further objects thereof, reference is made to the followingdescription, taken in connection with the accompanying drawing, and itsscope will be pointed out in the appended claims.

Referring now to the drawing:

FIG. 1 is a cross-sectional View of the shoe embodying the soleconstruction of the present invention and viewed along line I-I of FIG.2; and

FIG. 2 is a bottom plan view of a shoe showing the s-ole construction ofthe present invention.

Referring to the drawing, a shoe, such as a sneaker or the like, isshown generally at 10. Shoe 10 is il1ustrated with a conventional canvasupper 11, however, any suitable material may be used for the upper. Aconventional non-con-ductive calendered rubber -outsole 12 is secured toupper 11 around the upper periphery of the outsole. A foxing strip 13provides an additional bonding means between upper 11 and outsole 12.

Outsole 12 is of unitary construction and is relatively flat from thetoe to the .heel portion of the shoe. Outsole 12 is provided with afabric non-conductive sole binder 14 that is constructed of acombination friction binder stock and overlies the outsole 12 on theinner portion of shoe 10. A circular aperture 15 is cut through bothbinder 14 and outsole 12 in the ball portion of the shoe and aconductive rubber plug 16, the exact size of aperture 15, is molecularlybonded by v-ulcanization Within the aperture. A circular groove 17 ispressed or cut into the external surface of plug 16 to form an annularplug portion 18 which is in contact with the inner periphery of aperture15 formed in outsole 12. A relatively ilexible central plug .portion 19is also formed by groove 17.

A similar aperture 20 is cut through the heel portion of outsole 12 andbinder 14 and has a conductive rubber plug 21 located therein. Plug 21also has a groove 22 pressed or cut into the ground engaging portionthereof to form an outer annular plug portion 23 and a central ilexibleplug portion 24.

There are many conductive rubber compounds that are usable with itsinvention, however, it is preferred t-o use a compound that will berelatively ilexible when vulcanized. The compound preferred for 'use forall of the conductive rubber elements of the present improved soleconstruction is set forth below, wherein the parts of each compound isrepresented by the number preceding that compound:

100.0 MBlSH-Brown crepe (natural rubber) #4. 0.31 Lurex (zinc laur-ate).

44.4 Vulcan-XCR Black (carbon black).

13.3 Coray oil #4U-(naphthenic oil).

4.5 Zinc oxide.

.39 Ross wax (hydrocarbon wax).

.25 Flectol H (1,2-dihy-dro 2,2,4-

trimethylquinoline) .25 Aminox (reaction product of diphenylamine andacetone).

.17 ESEN (phthalic anhydride).

.19 Monex (tetramethy-lthiuram m-onosulfied).

.75 MBTS (benzothiozyl disulfide).

.44 DOTG (diorthotolyl quanidine).

A specic insole construction shown generally at 25 in FIG. l isincorporated into shoe 10 to provide a conductive interconnecting meansbetween the inner surfaces 26 and 27 of plugs 16 and 21, respectively,and the bottom of the wearers foot.

Insole 25 has an innermost foot engaging layer of fabric 30. Fabric 30may be any conventional, non-insulating fabric, such as Osnaburg. The4only requirement is that the fabric be of a nature that it readilyaccepts moisture from the wearers -foot thereby becoming conductive and,thus permitting the flow of electrical changes from the foot of thewearer to a layer 31 of conductive rubber cemented or otherwise joinedto the underside of fabric 30. A second layer lof conductive rubber 32directly `overlies fabric 14 and is bonded by vulcan'ization to surfaces26 and 27. A non-conductive fabric 33 separates conductive layers 31 and32 over most of the area of the sole construction but the layers 31 and32 are in intimate contact through an opening 34 cut through fabric 33.

A conventional foam rubber arch cushion 35 is provided in the shank andheel portions of the sole construction.

It will be apparent from the above description that an electricalgrounding path is provided bet-Ween the bottom of the wearers foot andthe ground via the interstices of fabric 30, conductive rubber layer 31,opening 3a conductive rubber layer 32, and either or both of theconductive -rubber plugs 16 and 21.

All of the rubber components of the improved shoe construction arefabricated before valcanization, therefore, all components are in thegum or unvulcanized state during assembly. Insole 25 is assembled byfirst securing fabric 3) to conductive gum` `layer 31. The bottom insolefabric layer 33 is then die-cut to provide opening 34 and fitted to theunderside of gum layer 31 with arch cushion 3S therebetween. Theconductive gum layer 32 is then placed over the bottom portion of fabriclayer 33 and the assembly is laminated, thereby pressing gum 32 throughopening 34 into intimate contact with conductive gum layer 31.

In the fabrication of shoe 10, the upper 11 is placed on a last andsecured to the insole assembly 25. Outsole 12 and `binder 14 withapertures 15 and 20 cut therethrough are then secured to the underside:of the insole 2S and the under-turnedperiphery of upper 11. Foxingstrip 13 is then positioned around the juncture of upper 11 and outsole12. The conductive gum plugs 16 and 21 are then manually placed intoapertures 15 and 20, respectively.

Referring t-o FIG. 1, an annular groove cutting tool 36 having a cuttingedge 37 andan opening 38 is then brought into position adjacent thegro-und engaging portion of the plugs and pressed into the plugs (asshown in broken lines in FIG. 1) to form grooves 17 and 22. Tool 35 maybe heated to provide smoother entry into plugs 16 and 21 and may also berotated to increase the cutting and pressing ability `of the tool. Theaction of tool 36 not only forms grooves 17 and 22 but also forces thesoft rubber of plugs 16 and 21 firmly against gum layer 32 and forcesthe annular plug portions 18 and 23 outwardly against the innerperiphery of -apertures and 20, respectively, Iformed in outsole 12.Since the rubber is unvulcanized andrelatively tacky, a very strong bondis formed between the plugs and the adjacent rubber surfaces. Uponcompletion of the 4grooving operation, the entire shoe assembly isvulcanized to form -a completed shoe.

It Iwill be apparent fromv the foregoing that, because of the firm bondaccomplished by the grooving operation, the plugs will not beappreciably affected by the repeated flexing of the outsole 12 duringwalking or other movements of the shoe. Furthermore, the centralflexible plug portions 19 and 24, which constitute the greater area ofthe ground engaging portion of the plugs, are free to flex withoutaffecting the bond between the plugs and lthe adjacent rubber surfaces.Although the diameters of grooves 17 and 22 are not critical, it isdesirable to form the grooves so that the diameters of the central plugportions are equal to at least one-half the overall plug diameters. Thisinsures that the central plug portions will have sufficient strength to-resist separation from the remainder of the plug, and yet, havesufficient flexibility to reduce the bending stresses between the plugsand the adjacent rubber surfaces to which `the plugs are bonded.

It will be apparent from the foregoing description that the presentinvention provides an improved conductive shoe construction that isespecially useful with flexible, thin-soled shoes; that is inexpensiveand simple to fabricate; that is constructed of materials that enablethe entire shoe to be .washed without harm to the shoe; and that iscompletely free of metallic parts.

While there has been described what is at present considered to be thepreferred embodiment of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and it is, therefore,aimed to cover all such changes and modifications as fall within thetrue scope and spirit of the invention.

Having thus described my invention, what I claim and desire to protectby Letters Patent is:

1. A conductive shoe comprising: a non-conductive thin, exible outsolehaving an aperture extending therethrough; a non-metallic flexibleconductive plug in said aperture, said plug having `a thicknessapproximating the thickness of said outsole, said plug having a groundengaging surface and an inner surface, said ground engaging surfacehaving an inwardly extending continuous groove forming an outer plugportion that is securely bonded to said outsole and a central exibleplug portion; and conductive means interconnecting said inner plugsurface with the innermost portion of said shoe, so that, saidconductive means and said plug form an electrical grounding path fo-rthe wearer.

2. A conductive shoe comprising: a non-conductive thin, exible outsolehaving an aperture extending therethrough; a flexible conductive rubberplug in said aperture, said plug having a thickness approximating thethickness `of said outsole, said plug having a ground engaging surfaceand an inner surface, said ground engaging surface having an inwardlyextending continuous Igroove forming an router plug portion that issecurely bonded to said outsole `and a central flexible plug portion;and conductive means interconnecting said inner plug surface with theimiermost portion of said shoe, so that, said conductive means and saidplug form an electrical grounding path for the wearer.

3. A conductive shoe comprising: a non-conductive thin, flexible outsolehaving an aperture extending through the heel portion thereof land anaperture extending through the `ball portion thereof; fiexibleconductive rubber plugs in said apertures each of said plugs having athickness approximating the thickness of said outsole, said plugs havingground engaging surfaces and inner surfaces, each of said groundengaging surfaces having an inwardly extending continuous `grooveforming an outer plug portion that is securely bonded to said outsoleand a central flexible plug portion; Iand conductive meansinterconnecting said inner plug surfaces with the innermost portion ofsaid shoe, so that, said conductive means and said plugs form anelectrical ygrounding path for the wearer.

4. The conductive shoe of claim 3 wherein said conductive meanscomprises a layer of conductive rubber overlying and connecting saidinner plug surfaces and having a molecular bond directly with said innerplug surfaces.

S. The conductive shoe of claim 3 wherein said outer plug portions havemolecular bonds around their peripheries directly with the innerperipheries of said outsole apertures.

6. A conductive shoe comprising: a non-conductive thin, flexible outsolehaving a circular aperture extending therethrough', a circularnon-metallic flexible conductive plug in said aperture, said plug havinga thickness approximating the thickness of said outsole, said plughaving a ground engaging surface and an inner surface, said groundengaging surface having an inwardly extending circular groove `formingan outer annular plug portion that is securely bonded to said outsolearound the inner periphery of said aperture, and a central flexible plugportion; and conductive egos/19a means interconnecting said inner plugsurface with the innermost portion of said shoe, so that, saidconductive means and said plug form an electrical grounding path for thewearer.

'7. The conductive shoe of claim 6 wherein the diameter of said centraliieXible plug portion is equal to at least one-half of the overalldiameter lof said plug.

8. In a method of making a conductive shoe the steps of: providing anon-conductive outsole with a circular aperture extending therethrough;positioning a layer of conductive gum over the inner surface of saidoutsole; placing a circular conductive gum plug into said aperture;pressing a circular groove into lthe surface of said plug to form anannular plug portion and a central flexible plug portion, said pressingstep being effective to force said annular plug portion nrnly againstthe inner Iperiphery of said outsole aperture and to force the innersurface 6 of said plug tirrnly against said gum layer; and vulcanizingsaid shoe; whereby, said plug is molecularly bonded to said conductivelayer and said outsole.

MELTON O. HlRSHFlELD, Prima/y Examiner.

I. A. SLVERMAN, Assistant Examiner.

SAMUEL BERNSTEIN, Examiner.

1. A CONDUCTIVE SHOE COMPRISING: A NON-CONDUCTIVE THIN, FLEXIBLE OUTSOLEHAVING AN APERTURE EXTENDING THERETHROUGH; A NON-METALLIC FLEXIBLECONDUCTIVE PLUG IN SAID APERTURE, SAID PLUG HAVING A THICKNESSAPPROXIMATING THE THICKNESS OF SAID OUTSOLE, SAID PLUG HAVING A GROUNDENGAGING SURFACE AND AN INNER SURFACE, SAID GROUND ENGAGING SURFACEHAVING AN INWARDLY EXTENDING CONTINUOUS GROOVE FORMING AN OUTER PLUGPORTION THAT IS SECURELY BONDED TO SAID OUTSOLE AND A CENTRAL FLEXIBLEPLUG PORTION; AND CONDUCTIVE MEANS INTERCONNECTING SAID INNER PLUGSURFACE WITH THE INNERMOST PORTION OF SAID SHOE, SO THAT, SAIDCONDUCTIVE MEANS AND SAID PLUG FORM, AN ELECTRICAL GROUNDING PATH FORTHE WEARER.